CA3077840A1 - Passive and forced air cooling for fresh produce - Google Patents

Abstract

Cases and containers for cooling produce may be cooperatively designed to provide cooling efficiencies in both passive ventilation and forced air cooling environments. Each container may include an element for helping form an opening or ventilation funnel within the center area of the cases, with a corresponding opening in the same arca of the case for allowing cooling fluid to pass therethrough. Further, each container may include an element for parsing or dividing incoming forced cooling fluid into both the lid and the base. In some versions of the containers, the air may be divided based at least in part on the design of the container, including the proportions of the containers lid to base structure. In this way the forced cooling fluid may be proportionately passed into the overall container to more efficiently cool the produce therein.

Description

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Page: 4 PASSIVE AND FORCED AIR COOLING FOR FRESH PRODUCE
BACKGROUND
The present invention relates to vented rigid plastic produce containers and the corresponding corrugated or plastic master shipping tray. More particularly, the present invention relates to a system or method of improved cooling of fresh produce held within such containers in both a passive stacked ventilation environment such as a field or cooling dock and in a horizontal forced air cooling system. In addition, the present invention also relates to the creation of a new preferred case configuration with improved synchronized venting structures, unique air flow pathways, increased pallet cube, and superior cooling.
Horticultural crops are living organisms after harvest and must remain alive and healthy until they are processed or consumed, The energy needed to stay alive comes from food reserves in the produce through a process called respiration. Heat energy is released during respiration; however, the rate of release depends on the type of produce, maturity, injuries and internal temperature. Of these factors, produce temperature has the most influence on respiration. Rapid, uniform cooling immediately after harvest to remove field and product heat helps slow respiration and provide a longer shelf life. As a rough guide, a one-hour delay in cooling reduces a produces shelf life by one day. Although this is not true for all crops, it applies to very highly perishable crops during hot weather.
Lowering the temperature also reduces the rate of ethylene production and moisture loss, as well as the spread of micro-organisms and deterioration from injuries to the fruit's surface.
Berry crops, that grow in warm to hot weather, including strawberries, raspberries, blackberries, and blueberries are valuable and highly perishable commodities with a high rate of respiration. Of all these berry crops only blueberries are picked, sorted by size, and pre-cooled prior to packaging into vented rigid plastic containers of various sizes and shapes for sale. All other berry commodities arc field packed directly from the plant or bush into vented rigid retail packaging that trap both field heat and product heat generated by core fruit temperature and respiration. These vented retail packages are often referred to as "clamshells" based on the nature of these containers being of a hinged middle with both a =
base and lid. These containers are the most widely used packaging products to deliver berry PAGE 4114 RCVD AT 41812020 1:20:07 PM [Eastern Daylight Time)*
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crops and other produce commodities from the field to the consumer's refrigerator; billions of containers are packed each year worldwide, Both the box/master ease and the clamshells are vented to draw out the heat of the produce post-harvest to a "7/8" ratio as fast as possible in a process known as forced air cooling to control the rate of respiration and decay of the produce. There are three main types of forced air cooling (F.A.C.) with tunnel or straight horizontal Airflow systems, column vertical airflow systems, and serpentine vertical! horizontal airflow systems. Forced air cooling with tunnel or straight horizontal airflow systems are the most common with berry crops. In this system, a fan generates a vacuum either directly into a pallet or into a tunnel separating a multi pallet system. The top and the ends of the pallets are tarped to reduce short circuit air flow during the cooling process. This suction or vacuum is intended to draw out the hot or warm air from the produce and suck out all the trapped field heat, replacing it with cold air from the cooler.
A "7/8" ratio is the industry standard when cooling berry crops, meaning the time needed to remove seven-eighths (87.5%) of the temperature difference between the initial temperature of produce and the temperature of the cooling medium (for forced air cooling systems, the cooling medium is refrigerated air ranging from 32-36 degrees).
The time is measured from the moment produce is first placed in the forced-air cooler to the moment it reaches the desired temperature. Achieving "7/8'' cool time ensures most of the field heat and core product heat have been removed, the respiration rate of the produce has been lowered and the produce is very close to its optimum holding temperature. In .
theory, produce never reaches the cooling medium temperature. However, the "7/8" cooling process is intended to get produce as close as practical to the temperature of the cooling medium before release for sale.
Considering that most berry crop production is tied to warm or hot daily temperatures and long exposure to sunlight, the largest seasonal volumes will also coincide with warmest and longest days. Therefore, the greatest production of any berry crop will be tied to the late spring and early summer months of the year where production often exceeds available cooling capacity and thus increasing cooling times and respiration rates.
During the peak of the season, picking and cooling times can often range from 1.5 to 'I hours per pallet creating poor conditions for fruit. Often pallets of fresh berries wait outside the cooling facility on the dock in shaded area for hours until a free spot opens up inside the cooler to start the "7/8"

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Page: 6 cooling process. In such a delayed cooling environment, ripe fruit is often left on the plant or bush and never harvested due to the high perish rate and long cooling times.
The two main components that can reduce cooling times during these peaks are the produce box/master case/returnable plastic container and the rigid plastic container.
However, produce boxes are manufactured by paper converters or injection molded plastic manufacturers while the plastic rigid containers arc made by manufacturers that convert rigid plastic through a process known as thermoforming. These three businesses don't work in parallel to create the best uniform cooling process, but rather have separate engineering and development groups that work within their own processes to design, engineer, and bring to market the most cost effective product with little understanding of the process as to how these components can work together as one unit to cool fruit, more efficiently.
Growers often purchase their rigid packaging needs and boxes based on price, availability, and service, not based on any fundamental link between the box ventilation of one company and the clamshell design or ventilation of another company. This link could help save or capture millions of dollars each season based on improving cooling times, increased product availability, superior product quality, better shelf life, and by lowering costs.
Ventilation patterns of produce boxes/ master eases and rigid plastic containers may differ greatly across the industry, but all of the commodity boxes/containers and commodity clamshells have a uniform shape and size that is of a fixed length, width, and height to accommodate predetermined packaged units of saleable fruits or vegetables at retail.
Moreover, the USDA has determined that all packaged produce must be priced based on weight or cubic volume with specific regulations that are controlled and policed by a division of the USDA called Weights and Measures. Underweight packages may result in high fines, penalties, and even the suspension or termination of the grower or shippers' P.A.C.A. licenses.
Some basic weights of measure for-the berry industry are the 6 oz., 12 oz., 11h. 18 oz., 21b., and the 41b. club store packages. The USDA also states that the weight on the package must "weigh out" not only at the grower level but all the way through distribution, sale at retail, and finally on to the consumer's refrigerator.
The standardization of corrugated boxes/trays/returnable plastic containers and the internal packaging units therein (clamshells) relates to the standard produce pallet being of

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Page: 7 48x40 inches with a specific number of boxes fitting on each layer or tie of the pallet. There are several main box configurations for the produce industry that have been developed over the last 3 decades to maximize cube, increase units per pallet spot, as well as truckload volume to reduce the impact of freight on the overall cost of produce to the consumer. Within the field packed berry category there are a number of box configurations that have become standard within the industry with the 5, 6, 8, and 12 down con figurations becoming the most prevalent. The strawberry industry has a preferred 6 down corrugated box footprint with 8 x 1 lb. strawberry "clamshells" within, with the average retail unit dimensions of 7.0" to 7.5" in length, 4.7" to 5.0" in width, and 3.0" to 3.50" in height, with an average corresponding box configuration of 20 inches in length, 16 inches in width, and 3.5 to 3.75 inches in height. This configuration is known as the 6-down box configuration with 8 x 1lb.
strawberry "clamshells"
within or the "1 lb. 6 down" configuration. In addition to the configuration of the pallet being standardized, the arrangement of the internal packaging or "clamshells" within are always identical regardless of manufacturer, as each clamshell design and shape is made for a specific box size, a unit of product weight, and unit fit into the box by number of rows and counts per row within the box.
In addition to the preferred 6 down 1 lb. strawberry configuration being the standard pallet layout, it is also the standard case unit by which most retailers purchase, set margins, track spoilage rates, track profit, monitor case turns at store level, estimate seasonal volumes, and track and process many other important retail data. For example, a major retail chain like Walmarte, with over 2,500 stores in the U.S. and Puerto, must have several produce buying groups working from one common ordering and buying platform in order to be efficient and track all relevant data with regards to perishable commodities. The inventory management and procurement platforms often notify the retail buyer daily or even hourly, in some eases, of how much product is available by case and price within their network of growers and what product is available to distribute out to stores from their regional produce warehouses.
Managing this intricate system of supply and demand on perishable fresh produce is a very difficult process. In order to achieve the most fluid system of fresh produce without gapping or overloading the system with perishable product that can remain at store level longer than expected resulting in high shrink rates and spoiled product, retail buyers rely heavily on the standardization of their supply chain. Therefore, it is most advantageous for growers to

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Page: 8 follow the industry standard when making packaging decisions for their crop.
Some packaging companies design and develop new corrugated footprints, such as the 9 down configuration, with new internal packaging counts of 6 or 12 instead of the standard 8 retail units, and tout various advancements in cooling, product density, and cube efficiencies only to be overlooked by the general marketplace, to a large degree, due to the considerable inertia and history with the standard 6 down configurations with 8 retail units within berry crops such as strawberries.
Therefore, it would be most advantageous to both the retailer and the berry grower if packaging companies focused their innovation efforts within the existing and accepted industry standard 6 down configuration framework or develop a new 6 down configuration as depicted within this invention that alters the dimensions and directional airflow of the system but does not change the layers on the pallet, or units within the case.
The Corrugated Box or Returnable Plastic Container (RPC) The fundamental purpose of a corrugated box or plastic master carton is to deliver fresh fruits and or vegetables from the field to the market for purchase. There are several key factors that contribute to the overall success of its purpose:
1. The boxIcontainer provides a vehicle for stacking packages of product or whole produce from the field in an organized, stacked, and protected shipping format.
2. The box/container provides the initial horizontal ventilation structure and air now method for cooling the fruit or vegetables inside it. How these venting structures are cut and line up with the clamshell containers or whole produce inside is the most critical function of the box when attempting to cool the product in the most efficient and uniform method.
3. The box provides a transfer of air flow from the cooler into the rigid plastic containers within to cool the held fruit. It must also draw or transfer the air flow to the next box/container on the horizontal pallet to continue the process.
4. Air transfer within the box/container may include both vertical and horizontal air flow or transfer vents that could assist in an even and uniform cooling process. It is critical to review both directional air flows to maximize stacked ventilation and create the most effective method of cooling.

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Page: 9 It is also critical to discuss the manufacturing and forming of the corrugated master tray or "produce box" when reviewing how the box will perform in conjunction with the held retail rigid plastic, "clamshell,' units within. The manufacturing process begins with varying grades of container hoards which are represented as "the medium" (the fluted middle layer) and "the linerboard" (the flat facings of the board). These two types' of board not only differ in function and purpose but also are made from different types of trees as well. After the liner and the medium are combined by use of a cornstarch based adhesive to form a single faced web in a single facer machine, the web enters a double gluer machine and double backer machine that bonds the liner to the single web creating the completed board. The corrugate board is then slit and scored to the specifications required as well as continues to the cut off knife where it is cut to the specific dimerisions of the requested board. The sheets arc then stacked and prepared for shipment to the converting plants.
There arc two main types of converting machines, the rotary die cutter and flexo folder gluer machine. Both play a role in adapting sheets of corrugate into produce boxes including printing designs and branding, cutting to proper dimensions, folding and gluing corners, and flaps and side walls. This last step has the greatest potential for variance with regards to the final formed tray. Unlike rigid plastic containers that are thermoformed by a single and exact mold and matching trim press, the corrugated box uses hot melt glue in between folded corners and flaps to hold its shape and dimensions. The variance in internal dimensions is critical as even a slight variance ranging from 118 to 1/64 of an inch on each corner of the tray may create a loose fitting internal packaging arrangement of "clamshells"
and thus create a failed air circuit in between clamshells within the case.
Failed air circuits are the leading cause of air flow passing through the case without penetrating the ventilation structures of "clamshells" and thus increasing cooling times and decreasing efficiencies.
After the sheet is converted into a box it is again stacked, palletized and readied for shipment to the grower, or a packaging company that will do the final assembly for the grower. It is here at final assembly where printed and branded corrugated boxes receive the addition of stacked sets of empty rigid plastic containers. After the corrugated boxes are filled with the predetermined size and number of "clamshells", the entire package is ready to be shipped to the PAGE 9114* RCVD AT 4/8120201:20:07 PM [Eastern Daylight Time]
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, Page: 10 The Rigid Plastic Vented Produce Container or "Clamshell"
The fundamental purpose of a "clamshell" (or "punnet") is to deliver a specific weight or measure of fruits and or vegetables from the field to the market for sale.
There are several key factors that contribute to the overall success of its purpose: .
"Clamshells" provide a uniform packing unit with a weight specific size which makes it possible to pack, cool, ship, merchandise and sell at retail. Clamshells provide an extra layer of protection for fruit and or vegetables from the field to the market and are an improvement over pulp open trays or injection molded open top baskets.
Clamshells utilize clear plastic to help identify the product quality and ripeness of fruit to consumers. Most designs include: ribbing or smooth wall structures that ensure the package will stack al. retail, a secure closure lock that holds the container together both before and after opening and reelosing multiple times, a ventilation pattern designed to cool fruit within, and a label platform for brand or grower identification. These are the main contributing factors that make it the method of choice for the produce industry today.
The most overlooked attribute of the clamshell is its ability to cool the fruit effectively and uniformly to reduce produce respiration rates and increase the product's shelf life. With California being the largest berry growing state in the United States, berries are often picked, cooled, and then shipped all the way across the country for sale. Therefore, the greater the shelf life, the greater market opportunity for the grower.
All these attributes are critical to the functionality and performance of these containers;
however, for over 25 years, the standard thermoformed clamshell design for all fruit or vegetable crops utilizes a tapered wall both on the lid and the base of the container which has proven to create a failed airflow circuit within the box/master case/RPC container. The tapered nature of the thermoformed clamshells can't be changed as the draft angle helps to form the parts, stack the parts together during transit, and enables the parts to be de-nested for labeling application. All these features and functions of the container makes it possible to manufacture a light weight and inexpensive package as not to burden the consumer with expensive packaging on food items.
There is also a greater gap or "V channel" in-between the clamshells as the draft angle is increased, so the taller the clamshell the greater the failed circuit of air becomes which affects cooling times and increasing product respiration rates. The "V
channel" is the space in between each row of clamshells and it is commonly referred to as a "V"
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Page: 11 true shape of the channel is an inverted V-shape. 'This inverted v-shaped channel will be referred to hereinafter as the "V" channel.
The greater the draft angle on the side walls the greater the gap in between the "clamshells." In addition, the longer the row of containers the larger the failed air circuit.
The average clamshell has an overall base height of 2.75-3.00 inches with a draft angle of 8-degrees, creating a 35-50% failed circuit within the box. These failed circuits occur when cold air is pulled inside the box/container and bypasses the hot fruit or vegetable inside the "clamshell" by taking the path of least resistance through the "V channels"
and thus following the vacuum or suction back out of the box/container. The "V channels" in-between the clamshells on both the top and the bottom of the clamshells will always be the path of least resistance regardless of the shape, location, and size of the, two-dimensional side vents within the corrugated box or RPC. In addition to the "V" channels created on the outside of the packages, there also exists some "clamshell" designs with bottom pathways or concaved air flow channels. These pathways or concaved channels do offer some additional ventilation into the bottom of the package, however, they also provide a larger center failed air circuit, or open circuit within the case, as most of the airflow rushes past the 90-degree ventilation apertures without a significant pull or draw extending up and into the center of the package.
An example of this can be seen in U.S. Patent No. 8,424,701. The "tunnel vent" or bottom "V" channel creates a larger than necessary bottom opening, or open circuit, that greatly reduces the efficiencies of a closed or non-connected bottom ventilation ramp or bridge.
Combined System Produce Box/RPC and Internal Rigid Parts The corrugated box or RPC must work together with the internal packaging to create a total system of air flow, cooling, and respiration control. If one or more of the properties are not aligned together and thus not working as a complete system, the end result will most likely be a failure (a short circuit of air flow) which can lead to an increase in cooling times and poor quality of fresh produce. Considering that the draft angle of all clamshells is a fundamental design feature but also a fundamental design flaw when cooling fruit or vegetables inside a box with forced air cooling, the "V channels" must be blocked or air must be redirected away from them to close the failed circuit and direct air into the clamshell's PAGE 11114* RCVD AT 41812020 1:20:07 PlyllEastem Daylight Timel*
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Assuming the "V channels" in-between the clamshells can be blocked either by thc design of the corrugated paper or plastic master shipping ease or by a secondary component added to the master case, a unique venting structure and pattern thereof must still be designed into the rigid plastic container to harness the newly directed airflow to create the most effective cooling method or process possible within the combined system. Most of the current ventilation patterns within rigid plastic containers on the market today use a straight down punch method that creates a punch, hole, or side wall vent at the base of a tapered or chamfered ribbed structure. By the nature of these ribbed structures and the current punch and die system used to create them, the ventilation patterns run along a horizontal plane around the perimeter of the container both on its base and lid; however, this pattern or system of ventilation creates no directional airflow or draw into the clamshell itself.
Most of the airflow surrounding the container simply bypasses the outer perimeter front facing venting structures by taking the least path of resistance and therefore creating a failed air circuit which produces little actual cooling of fresh produce inside the container. Containers that don't rely on any number of side wall ventilation apertures but rather on a system of linking the box air flow directly into the container through a large side air vent with a concaved base channel, also have challenges with failed air circuits present in the surrounding "clainshc,'Ils" due to case dimensional variances during ease erecting, as well as the failed air circuit present within the base concaved channel or pathway. Additionally, the loss of side ventilation apertures in the corners of the container can create hot spots and form condensation against side walls, both prior to and after the cooling process, and therefore subject produce to increased respiration rates over time.
As each produce box or returnable plastic container manufacturer touts their own unique ventilation pattern and the benefits or advantages therein so does each rigid plastic manufacturer. However, since the mid 1990's, both the University of California Davis and the University of Ontario Canada have concluded that the number of and size of vents have little overall effect on reducing both cooling times and respiration rates. An increase in vent size and number of vents on rigid containers simply don't equate into faster cooling times and may increase cooling times. Most manufacturers of rigid plastic containers, as well as growers alike, ignore these studies and follow the disproved theory that more vents are better when designing and developing air flow systems. The underlining problem that exists with vacuum PAGE 12114* RCVD AT 41812020 1:20:07 PM [Eastern Daylight Time]
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Page: 13 cooling is that air will take the path of least resistance when pulled through the box or master case so simply increasing the vent size and number of vents on rigid parts does little to do with increasing cooling times. If the air is not directed into the path of the vent structures, or if the vent structures themselves are two dimensional in nature causing air to flow past along a straight edge or line, the main underlining problem of the failed air circuit remains. Moreover, the current two-dimensional front facing venting structures are often blocked by denser fruit such as small strawberries, blackberries, raspberries, and most notably blueberries, causing little to no airflow being pulled from container to container. This problem causes fruit within rigid retail packages to be cooled from the outside in as the temperature of passing air slowly cools air and fruit within the container; therefore, a container that specifically directs airflow to penetrate the container at all layers of fruit and especially in between layers of fruit is key to have unobstructed airflow and cool fruit faster.
In greater detail, the overall misconception that more ventilation is better is compounded by the false perception that cooling from the outside of the package inward, or in some cases from the bottom of the clamshell upward, is the most effective method of cooling produce within. In most cases a dual method of cooling, from the inside out, and from the outside in, and at all layers of fruit would be the most efficient method of rapidly and evenly cooling produce within rigid plastic containers, however, there isn't a rigid retail unit, 'clamshell" or punnet on the market today that has these features incorporated into one design in combination with the master shipper box or RPC.
The only two clamshell designs that do utilize an air tunnel, channel, or pathway system to allow air to reach the center or bottom of the container are the system highlighted in U.S. Patent No. 8,424,701 and the system highlighted in U.S. Patent No.
6,644,494. Both systems use an air flow channel or channels by which to allow air to enter or pull from the bottom of the container. These tunnels or channels also have two-dimensional venting structures which are often located at the top or near top of tunnel structures at 90-degree angles from the air flow. It is very important to note that a 90-degree ventilation aperture at the top of a channel is very inefficient and a poor method of penetrating the bottom of the container, simple put there is no line of sight for air to penetrate the container arid instead must draw from radical 90-degree vents to accomplish vertical cooling. In addition, as air PAGE 13114* RCVD AT 4/8/2020 1:20:07 PM [Eastern Daylight Time]*
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Page: 14 travels at a high velocity, it fills all the available space within the tunnel or channel and will bypass the ventilation apertures located at the top 10% of the tunnel.
Moreover, the system venting structures and the relationships between the interior and exterior packaging (the "clamshells", and boxes or RPCs), must function in both a passive stacked ventilation environment and within a forced air cooling system.
Considering most current box and "clamshell" packaging solutions take little to no account of the two varying stages of cooling, (1) field passive ventilation, and (2) forced air cooling, it is advantageous to develop a combined package that performs under all conditions, especially considering that the passive ventilation environment may persist for several hours until the forced air process =
can begin.
Passive Ventilation Passive ventilation is the most overlooked of the two cooling stages. As the pallet of fruit or vegetables is being built at the field level, the Law of Convection needs to be considered to maximize the release of heat from the semi-closed pallet system.
By understanding the Law of Convection, a system of interlocking both box and "clamshell"
vents may be created to draw hot air up and out of the pallet and replace it with cooler air from the sides of the pallet.
Convection is the transfer of internal energy into or out of an object by the physical movement of a surrounding fluid that transfers the internal energy. Although the heat is initially transferred between the object and the fluid by conduction, the bulk transfer of energy conies from the motion of the fluid. Convection can arise spontaneously (or naturally or freely) through the creation of convection cells or can be forced by propelling the fluid across the object or by the object through the fluid. In our particular case the "fluid' is represented by air molecules surrounding the fruit or vegetable inside the rigid plastic container, "clamshell," as well as air molecules surrounding the internal rigid packaging v6thin the box or RPC.
To create turbulence within the pallet and to a greater extent within the vented rigid container to generate movement of hot air upward, vertical pathways or funnels must be created as well as an overall strategy of how to capitalize on the creation of low pressure within the pallet when hot air rises to continually create upward and inward movement of air. Stack PAGE 14114' RCVD AT 41812020 1:20:07 PM [Eastern Daylight Time)' SVR:OTT2350FAX01/9 " DNIS:3905 CSID: "ANI:8582003000" DURATION (mm-ss):10-04